Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is a second image thereof;

FIG. 3 is a third image thereof;

FIG. 4 is a fourth image thereof;

FIG. 5 is a fifth image thereof;

FIG. 6 is a sixth image thereof; and,

FIG. 7 is a seventh image thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-7. The process or period in which one image transitions to another forms no part of the claimed design. The broken lines represent the display screen and the remainder of the graphical user interface and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 